Chick-fil-A's chefs are free to experiment with all kinds of ingredients, except for one: iceberg lettuce.

"We have a mandate: never use iceberg lettuce," David Farmer, Chick-fil-A vice president of menu strategy and development, said in an interview from Chick-fil-A's test kitchen.

Farmer claims iceberg lettuce is tasteless and nutrionless, which is why he says he's banned the ingredient.

"It's at the bottom of the salad food chain," he says. "There is no nutritional value in iceberg lettuce."

Photos of Chick-fil-A's NYC store opening:

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Chick-fil-a October Manhattan restaurant opening

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Chick-fil-A has banned one ingredient from its restaurants

Pedestrians walk past a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

Chicken nuggets, french fries, and a fried chicken sandwich are arranged for a photograph during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

An employees gives chicken sandwich samples to guests during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

A employee picks up a fried chicken sandwich during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

An employee prepares chicken nuggets for guests during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

An employee prepares food for guests during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

Employees prepare fried chicken sandwiches for guests during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

Employees wash vegetables during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

Attendees take a selfie photograph with the Chick-fil-A mascot during an event ahead of the grand opening for the restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

French fries and a fried chicken sandwich are arranged for a photograph during an event ahead of the grand opening for a Chick-fil-A restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

The Chick-fil-A mascot rides an elevator during an event ahead of the grand opening for the restaurant in New York, U.S., on Friday, Oct. 2, 2015. Chick-fil-A, the Southern chicken-sandwich chain that has drawn both controversy and copycats over the years, has finally arrived in New York. The company will open a 5,000-square-foot (465-square-meter), three-level restaurant in Manhattan's Garment District that will be the chain's largest location in the nation. Photographer: Michael Nagle/Bloomberg via Getty Images

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Farmer said he's more supportive of nutrient-dense greens like kale.

"Our focus over the last couple years has been around health," he says. "We're seeing purchase behavior shift toward healthier items, so we're fully committed to providing more nutritional options for customers."

Farmer says he gets some inspiration for new menu items from frequent trips to New York.

"I travel to New York to check out new concepts and walk around trying food all day long until I can't stand to put anything else in my mouth," he said.

Chick-fil-A also keeps an eye on its competition, which includes traditional fast-food restaurants like McDonald's and Wendy's, as well as fast-casual chains like Panera Bread and Chipotle.